You do have to check the fare class you're getting on Expedia / Orbitz / etc. before booking, which isn't always easy to do. I once booked a well-priced AF ticket in N class without realizing it earned RDMs equalling only 25% of actual miles flown in the DL program (or perhaps it was NW back then). Anyway be careful, especially as Delta has cut EQM earnings on some ST partners / far classes.